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author | Ingo Molnar <mingo@kernel.org> | 2016-11-23 10:23:09 +0100 |
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committer | Ingo Molnar <mingo@kernel.org> | 2016-11-23 10:23:09 +0100 |
commit | ec84f0056711efe93f034c86dd65e0de8d3531ff (patch) | |
tree | 3e50d385d645487924bcac1f5fb33b496cda6dc0 /kernel/sched | |
parent | d03266910a533d874c01ef2ca8dc73009f2925fa (diff) | |
parent | 23400ac997062647f2b63c82030d189671b1effe (diff) | |
download | linux-stable-ec84f0056711efe93f034c86dd65e0de8d3531ff.tar.gz linux-stable-ec84f0056711efe93f034c86dd65e0de8d3531ff.tar.bz2 linux-stable-ec84f0056711efe93f034c86dd65e0de8d3531ff.zip |
Merge branch 'linus' into sched/core, to pick up fixes
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
-rw-r--r-- | kernel/sched/auto_group.c | 36 |
1 files changed, 28 insertions, 8 deletions
diff --git a/kernel/sched/auto_group.c b/kernel/sched/auto_group.c index a5d966cb8891..f1c8fd566246 100644 --- a/kernel/sched/auto_group.c +++ b/kernel/sched/auto_group.c @@ -111,10 +111,13 @@ bool task_wants_autogroup(struct task_struct *p, struct task_group *tg) { if (tg != &root_task_group) return false; - /* - * We can only assume the task group can't go away on us if - * autogroup_move_group() can see us on ->thread_group list. + * If we race with autogroup_move_group() the caller can use the old + * value of signal->autogroup but in this case sched_move_task() will + * be called again before autogroup_kref_put(). + * + * However, there is no way sched_autogroup_exit_task() could tell us + * to avoid autogroup->tg, so we abuse PF_EXITING flag for this case. */ if (p->flags & PF_EXITING) return false; @@ -122,6 +125,16 @@ bool task_wants_autogroup(struct task_struct *p, struct task_group *tg) return true; } +void sched_autogroup_exit_task(struct task_struct *p) +{ + /* + * We are going to call exit_notify() and autogroup_move_group() can't + * see this thread after that: we can no longer use signal->autogroup. + * See the PF_EXITING check in task_wants_autogroup(). + */ + sched_move_task(p); +} + static void autogroup_move_group(struct task_struct *p, struct autogroup *ag) { @@ -138,13 +151,20 @@ autogroup_move_group(struct task_struct *p, struct autogroup *ag) } p->signal->autogroup = autogroup_kref_get(ag); - - if (!READ_ONCE(sysctl_sched_autogroup_enabled)) - goto out; - + /* + * We can't avoid sched_move_task() after we changed signal->autogroup, + * this process can already run with task_group() == prev->tg or we can + * race with cgroup code which can read autogroup = prev under rq->lock. + * In the latter case for_each_thread() can not miss a migrating thread, + * cpu_cgroup_attach() must not be possible after cgroup_exit() and it + * can't be removed from thread list, we hold ->siglock. + * + * If an exiting thread was already removed from thread list we rely on + * sched_autogroup_exit_task(). + */ for_each_thread(p, t) sched_move_task(t); -out: + unlock_task_sighand(p, &flags); autogroup_kref_put(prev); } |